feat(axivity6): support for Axivity 6 (gyroscope data)

[aidanacquah]

This PR addresses #37 allowing for the parsing of AX6 device.

To do so, we follow changes made at openmovementproject/openmovement@570001c to address parsing of the AX6 device.

To test this is working as expected, we have 4 files:

1. A raw sample cwa captured from an Ax3 device
2. A raw csv file extracted from OmGUI for the cwa file in Part 1
3. A raw sample cwa captured from an Ax6 device
4. A raw csv file extracted from OmGUI for the cwa file in Part 3

We have tested to ensure:

1. actipy.read_device(file1) continues to work as expected
2. actipy.read_device(file1) produces acc values similar to file2
3. actipy.read_device(file3) works, while adding new gyroscope columns
4. actipy.read_device(file3) produces acc and gyro values similar to file4

Test system configuration:

Test1:

Test2:

Test3:

Test4:

Note: An error is reported stating the "data.npy file cannot access the file because it is being used by another process." however this error is not related to this work, and file reading works despite the error. I have therefore reported it in a New issue #41

[chanshing]

Awesome job @aidanacquah Thanks a lot for this!